Many operations are timing out during rebalancing

I tried adding a fourth server with similar specs to the cluster, and found that during the rebalancing, a large number of operations simply timed out after about 30 secs.

The same behavior was observed using the VBucketAware Python client, local Moxi servers and telnetting directly to the CB servers.

I was under the impression that if the client/Moxi hits a wrong server during rebalancing it's supposed to immediately return a "not my vbucket" error so it can immediately figure out the actual server to query?